The Making of the Atomic Bomb: 25th Anniversary Edition

by Richard Rhodes

The first of the two parts they titled “On the construction of a ‘superbomb’; based on a nuclear chain reaction in uranium.”1275 It was intended, they wrote, “to point out and discuss a possibility which seems to have been overlooked in . . . earlier discussions.”1276 They proceeded to cover the same ground they had previously covered together in private, noting that “the energy liberated by a 5 kg bomb would be equivalent to that of several thousand tons of dynamite.” They described a simple mechanism for arming the weapon: making the uranium sphere in two parts “which are brought together first when the explosion is wanted. Once assembled, the bomb would explode within a second or less.”1277 Springs, they thought, might pull the two small hemispheres together. Assembly would have to be rapid or the chain reaction would begin prematurely, destroying the bomb but not much else. A byproduct of the explosion—about 20 percent of its energy, they thought—would be radiation, the equivalent of “a hundred tons of radium” that would be “fatal to living beings even a long time after the explosion.” Effective protection from the weapon would be “hardly possible.”